US7646547B2ActiveUtilityPatentIndex 52
Three-unit zoom lens and image pickup apparatus equipped with same

Assignee: OLYMPUS IMAGING CORPPriority: Oct 12, 2007Filed: Oct 3, 2008Granted: Jan 12, 2010
Est. expiryOct 12, 2027(~1.3 yrs left)· nominal 20-yr term from priority
Inventors:KATAKURA MASAHIRO
G02B 15/143507G02B 15/143503G02B 15/177
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Claims
Abstract

A three-unit zoom lens includes, in order from the object side, a negative first lens unit G 1 , a positive second lens unit G 2 and a third lens unit G 3 , wherein during zooming from the wide angle end to the telephoto end the distance between the first lens unit G 1 and the second lens unit G 2 decreases and the distance between the second lens unit G 2 and the third lens unit G 3 changes. The first lens unit G 1 is composed of one negative lens component including, in order from the object side, a negative lens having a concave surface directed toward the image side and a positive lens having a convex surface directed toward the object side. The second lens unit G 2 includes at least one negative lens and a plurality of positive lenses, wherein at least three lenses among these lenses are cemented to adjacent lenses, the total number of lens components included in the second lens unit G 2 is two or less. The third lens unit is composed of one lens component composed of two or less lenses.
Claims

exact text as granted — not AI-modified
1. A three unit zoom lens comprising, in order from an object side thereof:
 a first lens unit having a negative refracting power; 
 a second lens unit having a positive refracting power; and 
 a third lens unit having a refracting power, wherein 
 during zooming from a wide angle end to a telephoto end, a distance between the first lens unit and the second lens unit decreases, and a distance between the second lens unit and the third lens unit changes, 
 the first lens unit comprises a negative lens component having a negative refracting power and including, in order from the object side, a negative lens having a concave surface directed toward an image side and a positive lens having a convex surface directed toward the object side, 
 the total number of lens components included in the first lens unit is one, 
 the second lens unit comprises at least one negative lens and a plurality of positive lenses, 
 at least three lenses among the lenses in the second lens unit are cemented to adjacent lenses, 
 the total number of lens components included in the second lens unit is two or less, 
 the third lens unit comprises a lens component composed of two or fewer lenses, and 
 the total number of lens components included in the third lens unit is one, 
 where the term “lens component” refers to a lens member whose surfaces that are in contact with air on an optical axis include only two surfaces, one being an object side surface and the other being an image side surface. 
 
   
   
     2. The three-unit zoom lens according to  claim 1 , wherein the negative lens component in the first lens unit has an aspheric cemented surface. 
   
   
     3. The three-unit zoom lens according to  claim 1 , wherein the negative lens component in the first lens unit has a spherical cemented surface. 
   
   
     4. The three-unit zoom lens according to  claim 1 , wherein the first lens unit satisfies the following condition:
   0.05 &lt;D   G1   /f   w &lt;0.8   (1) 
 
     where D G1  is a thickness of the first lens unit on the optical axis, and f w  is a focal length of the three-unit zoom lens at the wide angle end. 
   
   
     5. The three-unit zoom lens according to  claim 1 , wherein a lens component located closest to the object side in the second lens unit is a cemented lens component that satisfies the following condition:
   0.5&lt; f   G2C1   /f   w &lt;5.0   (2) 
 
     where f G2C1  is a focal length of the lens component located closest to the object side in the second lens unit, and f w  is a focal length of the three-unit zoom lens at the wide angle end. 
   
   
     6. The three-unit zoom lens according to  claim 1 , wherein the negative lens in the first lens unit satisfies the following condition:
     nd   G1L1 &gt;1.75   (3) 
 
     where nd G1L1  is a refractive index of the negative lens in the first lens unit. 
   
   
     7. The three-unit zoom lens according to  claim 1 , wherein the negative lens in the first lens unit satisfies the following condition:
   ν d   G1L1 &gt;60   (4) 
 
     where νd G1L1  is an Abbe number of the negative lens in the first lens unit. 
   
   
     8. The three-unit zoom lens according to  claim 1 , wherein the negative lens in the first lens unit has a biconcave shape that satisfies the following condition:
   −0.95&lt;( r   L11f   +r   L11r )/( r   L11f   −r   L11r )&lt;0.95   (5) 
 
     where, r L11f  is a paraxial radius of curvature of the object side surface of the negative lens in the first lens unit, and r L11r  is a paraxial radius of curvature of the image side surface of the negative lens in the first lens unit. 
   
   
     9. The three-unit zoom lens according to  claim 1 , wherein the positive lens in the first lens unit has a shape that satisfies the following condition:
   −40.0&lt;( r   L12f   +r   L12r )/( r   L12f   −r   L12r )&lt;−0.95   (6) 
 
     where, r L12f  is a paraxial radius of curvature of the object side surface of the positive lens in the first lens unit, and r L12r  is a paraxial radius of curvature of the image side surface of the positive lens in the first lens unit. 
   
   
     10. The three-unit zoom lens according to  claim 1 , wherein the following condition is satisfied:
   6 ≦N≦ 7   (7) 
 
     where N is the total number of lenses in the three-unit zoom lens. 
   
   
     11. The three-unit zoom lens according to  claim 1 , wherein a lens surface located closest to the object side in the second lens unit is an aspheric surface. 
   
   
     12. The three-unit zoom lens according to  claim 1 , wherein the second lens unit comprises a lens component including, in order from the object side, a positive lens, a negative lens and a positive lens. 
   
   
     13. The three-unit zoom lens according to  claim 12 , wherein the total number of lens components in the second lens unit is one. 
   
   
     14. The three-unit zoom lens according to  claim 1 , wherein the second lens unit comprises two lens components each of which has a cemented surface, and the total number of lens components included in the second lens unit is two. 
   
   
     15. The three-unit zoom lens according to  claim 14 , wherein each of the lens components in the second lens unit is a doublet. 
   
   
     16. The three-unit zoom lens according to  claim 1 , wherein during zooming from the wide angle end to the telephoto end, the second lens unit moves while satisfying the following condition:
   0.5&lt;Δ G 2/ f   w &lt;3.0   (8) 
 
     where ΔG 2  is the amount of displacement of the position of the second lens unit at the telephoto end from the position thereof at the wide angle end, and displacements toward the object side are represented by positive values. 
   
   
     17. The three-unit zoom lens according to  claim 1 , wherein the third lens unit has a positive refracting power. 
   
   
     18. The three-unit zoom lens according to  claim 17 , wherein the third lens unit has a biconvex shape. 
   
   
     19. The three-unit zoom lens according to  claim 17 , wherein the third lens unit consists of a biconvex positive lens. 
   
   
     20. The three-unit zoom lens according to  claim 1 , wherein the third lens unit has a negative refracting power. 
   
   
     21. The three-unit zoom lens according to  claim 1 , wherein focusing is performed by moving the third lens unit along the optical axis direction. 
   
   
     22. The three-unit zoom lens according to  claim 1 , wherein the position of the third lens unit at the telephoto end is displaced toward the object side with respect to the position of the third lens unit at the wide angle end. 
   
   
     23. The three-unit zoom lens according to  claim 1 , wherein during zooming from the wide angle end to the telephoto end, the third lens unit moves only toward the object side. 
   
   
     24. The three-unit zoom lens according to  claim 1 , further comprising an iris stop disposed between the first lens unit and the second lens unit. 
   
   
     25. The three-unit zoom lens according to  claim 1 , further comprising:
 an iris stop disposed between the first lens unit and the second lens unit; and 
 a flare stop disposed between the second lens unit and the third lens unit. 
 
   
   
     26. An image pickup apparatus comprising:
 a three-unit zoom, and 
 an image pickup element disposed on an image side of the three-unit zoom lens that converts an optical image formed by the three-unit zoom lens into an electrical signal, wherein the three-unit zoom lens comprises a three-unit zoom lens according to  claim 1 . 
 
   
   
     27. The image pickup apparatus according to  claim 26 , wherein the third lens unit moves while satisfying the following conditional expression (12):
   −0.80&lt;Δ D   g3   /Ih ( t )&lt;8.00   (12) 
 
     where ΔD g3  is displacement of the position of the third lens unit at the telephoto end from its position at the wide angle end, displacements toward the object side being represented by positive values, and Ih(t) is a maximum image height at the telephoto end. 
   
   
     28. The image pickup apparatus according to  claim 26 , further comprising an image transformation section that transforms, by image processing, the electrical signal, which contains a distortion due to the three-unit zoom lens, into an image signal in which the distortion is corrected. 
   
   
     29. A three-unit zoom lens comprising, in order from an object side thereof,
 a first lens unit having a negative refracting power; 
 a second lens unit having a positive refracting power; 
 a third lens unit having a positive refracting power, wherein 
 during zooming from a wide angle end to a telephoto end, a distance between the first lens unit and the second lens unit decreases, and a distance between the second lens unit and the third lens unit changes, 
 an iris stop that moves integrally with the second lens unit is further provided, 
 the first lens unit consists of one negative lens component having a negative refracting power and including, in order from the object side, a negative lens having a concave surface directed toward the image side and a positive lens having a convex surface directed toward the object side, 
 the total number of lens components included in the first lens unit is one, 
 the second lens unit comprises at least one negative lens and a plurality of positive lenses, 
 at least three lenses among the lenses in the second lens unit are cemented to adjacent lenses, 
 the total number of lens components included in the second lens unit is two or less, 
 the third lens unit consists of one positive lens component, and 
 the positive lens component in the third lens unit includes a lens that satisfies the following conditional expression (9) and the positive lens component in the third lens unit satisfies the following conditional expression (10):
   1.49 &lt;nd   3low &lt;2.4   (9) 
   −1.0&lt;( r   3a   +r   3b )/( r   3a   −r   3b )&lt;1.0   (10) 
 
 
     where, nd 3low  is a refractive index of a lens having the lowest refractive index for the d line in the positive lens component in the third lens component, r 3a  is a paraxial radius of curvature of an object side surface of the positive lens component in the third lens unit, and r 3b  is a paraxial radius of curvature of an image side surface of the positive lens component in the third lens unit,
 where the term “lens component” refers to a lens member whose surfaces that are in contact with air on the optical axis include only two surfaces, one being an object side surface and the other being an image side surface. 
 
   
   
     30. The three-unit zoom lens according to  claim 29 , wherein the third lens unit satisfies the following conditional expression (11):
   −0.40&lt; D   g3   /r   3b &lt;0.0   (11) 
 
     where D g3  is a thickness of the third lens unit on the optical axis. 
   
   
     31. The three-unit zoom lens according to  claim 29 , wherein the negative lens component in the first lens unit has a biconcave shape. 
   
   
     32. The three-unit zoom lens according to  claim 29 , wherein the negative lens included in the negative lens component in the first lens unit has a shape that satisfies the following conditional expression (15):
   −1.0&lt;( r   1na   +r   1nb )/( r   1na   −r   1nb )&lt;1.0   (15) 
 
     where, r 1na  is a paraxial radius of curvature of an object side surface of the negative lens included in the negative lens component in the first lens unit, and r 1nb  is a paraxial radius of curvature of an image side surface of the negative lens included in the negative lens component in the first lens unit. 
   
   
     33. The three-unit zoom lens according to  claim 29 , wherein focusing operation from a long distance to a short distance at the wide angle end is performed by moving the third lens unit toward the object side, and the first lens unit, the second lens unit and the third lens unit satisfy the following conditional expression (13) in a state in which the zoom lens is focused on a longest distance at the wide angle end:
   2.0&lt; D   12   /D   23 &lt;8.0   (13) 
 
     where D 12  is the distance, on the optical axis, between the first lens unit and the second lens unit at the wide angle end, and D 23  is the distance, on the optical axis, between the second lens unit and the third lens unit at the wide angle end. 
   
   
     34. The three-unit zoom lens according to  claim 29 , wherein the negative lens component in the first lens unit has an aspheric cemented surface. 
   
   
     35. The three-unit zoom lens according to  claim 29 , wherein the negative lens component in the first lens unit has a spherical cemented surface. 
   
   
     36. The three-unit zoom lens according to  claim 29 , wherein the first lens unit satisfies the following conditional expression (14):
   −0.70&lt; D   g1   /f   1 &lt;−0.075   (14) 
 
     where D g1  is a thickness of the first lens unit on the optical axis, and f 1  is a focal length of the first lens unit. 
   
   
     37. The three-unit zoom lens according to  claim 29 , wherein the second lens unit consists of one cemented lens component. 
   
   
     38. The three-unit zoom lens according to  claim 37 , wherein the one lens component in the second lens unit is a lens component including, in order from the object side, a positive lens, a negative lens and a positive lens. 
   
   
     39. The three-unit zoom lens according to  claim 29 , wherein the second lens unit consists of two cemented lens components. 
   
   
     40. The three-unit zoom lens according to  claim 39 , wherein the second lens unit consists of two cemented doublet lens components. 
   
   
     41. The three-unit zoom lens according to  claim 29 , wherein the positive lens component in the third lens unit is a single lens. 
   
   
     42. The three-unit zoom lens according to  claim 29 , wherein the positive lens component in the third lens unit is a cemented lens component. 
   
   
     43. The three-unit zoom lens according to  claim 29 , wherein the total number of aspheric surfaces in the third lens unit is at most one.
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